Rashivalaya Yantra, Jantar Mantar, Jaipur, Rajasthan, India
Completed in 1734 this is an astronomical abservatory built by Maharaja Sawai Jai Singh II. It houses the world's largest collection of stone asttronomical instruments. He used it to study planetary positions and predict eclipses etc, using naked-eye observations. The name is derived from two Sanskrit words Jantar meaning instrument and Mantar meaning calculation.
The Rashivalaya Yantra is a collection of 12 distinct smaller sun dials, each dedicated to one of the 12 zodiac constallations. Based on the large Samrat Yantra, each of the of the instruments features a gnomon and quadrants - the gnomon's slope and the angle of the quandrants vary to align with specific constellations.
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